【公開日：2025.08.01】【最終更新日：2025.08.01】
課題データ / Project Data
課題番号 / Project Issue Number
22MS5024
利用課題名 / Title
Fabrication of plasmonic chiral nanostructure
利用した実施機関 / Support Institute
自然科学研究機構 分子科学研究所 / IMS
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）物質・材料合成プロセス/Molecule & Material Synthesis（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）マテリアルの高度循環のための技術/Advanced materials recycling technologies（副 / Sub）次世代ナノスケールマテリアル/Next-generation nanoscale materials
キーワード / Keywords
Nanomaterial, chiral, plasmonics
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
AHN HYO-YONG
所属名 / Affiliation
分子科学研究所 メゾスコピック計測研究センター 繊細計測研究部門（岡本G）
共同利用者氏名 / Names of Collaborators Excluding Supporters in the Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Supporters in the Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Chirality, a concept used to describe objects that lack mirror symmetry, is important for understanding a variety of physical and chemical phenomena. However, creating chirality and chiro-optical effects remains a significant challenge. In particular, nanosized materials have unique properties different from their bulk counterparts, requiring a different approach to generating and controlling chirality. As an attempt to manipulate and utilize the nanoscale chirality, we aimed two separate approaches, 1) the generation of highly chiral optical responses using peptide-directed chiral nanoparticles and 2) the development of a method to simultaneously generate chiral structures and chiral optical response using a local electromagnetic field. In this research project, we investigated the morphology of the chiral nanostructures fabricated by these two approaches, and utilize them to achieve fine control of the nanofabrication method and elucidate geometry-dependent local chiro-optical responses.
実験 / Experimental
The chiral “432 helicoid III” nanoparticle was synthesized in accordance with the previous report [Lee, Ahn, Nam et al., Nature 556, 360 (2018)]. For SEM observation, the solution of the nanoparticle was centrifuged and re-dispersed twice with deionized water and drop-casted on the silicon substrate. For the fabrication of a chiral hybrid nanorod structure, Au@Ag nanorod particles (aspect ratio: 2~3) were used as hosts of photochemical reaction. The nanoparticles were spin-coated on ITO substrate and immersed in divinylbenzene (DVB) monomer medium. Then, a circularly polarized laser beam with 660nm wavelength was focused on the nanoparticle. Under the laser beam exposure (~30 seconds), a local polymerization reaction occurred at the surface of the nanoparticle and eventually formed polymer structures of chiral morphology. To analyze the morphology of the chiral hybrid nanorod structure, the remaining monomer was carefully washed with acetone and isopropyl alcohol, and subsequently, the substrate was dried for SEM observation.
結果と考察 / Results and Discussion
A typical shape of the chiral Au nanoparticles, i.e., Helicoid III NPs, was illustrated in the scanning electron micrograph (SEM) image and 3D model (Figure 1). The Helicoid III NPs have a highly twisted geometry directed by peptide-directed synthesis. During the seed-mediated growth of octahedral seed nanoparticles, a small amount of peptide molecules, L-glutathione, was added to interact with chiral high-Miller-index planes of gold nanoparticle surfaces. The enantioselective binding effect of the peptides and gold surfaces led to the asymmetric growth of crystal facets, finally forming a characteristic pin-wheel-like structure at the 6-faces of the 180-nm-sized nanocubes. In particular, they show concave “chiral gap” structures that deeply carve into the central direction of nanoparticle. This chiral gap developed on all sides of the nanoparticle surface can lead to strong intra-particle coupling of electromagnetic fields and governs the optical property of helicoid NP. The synthesized nanoparticle was utilized to generate circularly polarized emission of Au helicoid nanoparticle. The photoluminescence was generated by the excitation of the Au nanoparticle using a tightly focused near-infrared laser. The sample was prepared by spin-coating the nanoparticle solution on a fused silica substrate. We found a clear difference of emission intensity between two circular polarization states, where the intensity of RCP emission is almost 2-times higher than that of LCP emission. Detailed analysis on this result will be described in the separate manuscript, which will be published soon.In addition to the chemically synthesized chiral nanoparticle, the localized photochemical reaction directly induced by chiral electromagnetic field was also adopted to fabricate chiral structures in nanoscale. We chose Au@Ag core-shell nanorod particle as a “host” of localized photochemical reaction. Although the overall chiroptical response averages to zero due to the structure is achiral, the numerical simulation reveals that this anisotropic structure shows an exceptionally large contrast under the circularly polarized mode in a local area (Figure 2a) with absolute g-factor values greater than ±1 at the corners. As an initial trial, we employed a photopolymerization reaction induced by plasmonic hot-electron, which is recently discovered by other groups [ACS Photonics 4, 1453 (2017)], to demonstrate our approach. Under the circularly polarized illumination, the polymerized structure accurately replicated the actual location and shape of the electromagnetic chiral hotspot (Figure 2b). We named this metal-polymer hybrid structure as “chiral hybrid nanorod” structure. The fabricated polymer structure not only created chiral geometries but served as a matrix for the chiral light-matter coupling by embedding secondary materials inside. Currently, we are further extending this approach to various types of secondary materials and photochemical reactions and making efforts to observe chiroptical response in this system. We believe that this approach can provide a new insight to design efficient chiral light-matter interaction system.
図・表・数式 / Figures, Tables and Equations
Fig 1. SEM image of 432 helicoid III nanoparticle and corresponding 3D model.
Fig 2. (a) E-field distribution near the nanorod particle under the illumination of circularly polarized light. (b) SEM image of chiral hybrid nanorod.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
-
Hyo‐Yong Ahn, Highly Chiral Light Emission Using Plasmonic Helicoid Nanoparticles, Advanced Optical Materials, 12, (2024).
DOI: https://doi.org/10.1002/adom.202400699
-
Junsuke Yamanishi, Optical gradient force on chiral particles, Science Advances, 8, (2022).
DOI: 10.1126/sciadv.abq2604
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件